Temperature and pressure dependence of the NCO + C2H2 reaction

The reaction of NCO(X2Π) radicals with C2H2 was investigated under pseudo-first-order conditions at 20 and 100 Torr total pressure as a function of temperature in the range 298–981 K. NCO radicals were generated by excimer laser photolysis of CINCO/Ar mixtures and were detected by laser-induced fluorescence. In the temperature range 296–597 K the measured rate constants exhibit a positive temperature dependence which is described by the Arrhenius equation kNCO+C2H2(T) = (2.4 ± 0.1) × 10−12 exp[−(7.6 ± 0.2)/RT] cm3 s−1, with EA in units of kJ/mol. In addition, the rate constant of the reaction NCO + C2H2 was found to be pressure indenpendent in the range 10–560 Torr at 298 K within experimental error.